JP3835241B2 - Exhaust gas purification device for internal combustion engine - Google Patents

Exhaust gas purification device for internal combustion engine Download PDF

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JP3835241B2
JP3835241B2 JP2001317222A JP2001317222A JP3835241B2 JP 3835241 B2 JP3835241 B2 JP 3835241B2 JP 2001317222 A JP2001317222 A JP 2001317222A JP 2001317222 A JP2001317222 A JP 2001317222A JP 3835241 B2 JP3835241 B2 JP 3835241B2
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filter
temperature
exhaust
internal combustion
combustion engine
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JP2003120373A (en
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久 大木
正明 小林
尚史 曲田
大介 柴田
秋彦 根上
忍 石山
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トヨタ自動車株式会社
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    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01NGAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N3/00Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
    • F01N3/02Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust
    • F01N3/021Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust by means of filters
    • F01N3/023Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust by means of filters using means for regenerating the filters, e.g. by burning trapped particles
    • F01N3/025Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust by means of filters using means for regenerating the filters, e.g. by burning trapped particles using fuel burner or by adding fuel to exhaust
    • F01N3/0253Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust by means of filters using means for regenerating the filters, e.g. by burning trapped particles using fuel burner or by adding fuel to exhaust adding fuel to exhaust gases
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01NGAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N3/00Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
    • F01N3/02Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust
    • F01N3/021Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust by means of filters
    • F01N3/022Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust by means of filters characterised by specially adapted filtering structure, e.g. honeycomb, mesh or fibrous
    • F01N3/0222Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust by means of filters characterised by specially adapted filtering structure, e.g. honeycomb, mesh or fibrous the structure being monolithic, e.g. honeycombs
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01NGAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N3/00Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
    • F01N3/02Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust
    • F01N3/021Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust by means of filters
    • F01N3/023Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust by means of filters using means for regenerating the filters, e.g. by burning trapped particles
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01NGAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N3/00Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
    • F01N3/08Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
    • F01N3/0807Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by using absorbents or adsorbents
    • F01N3/0821Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by using absorbents or adsorbents combined with particulate filters
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01NGAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N3/00Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
    • F01N3/08Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
    • F01N3/0807Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by using absorbents or adsorbents
    • F01N3/0828Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by using absorbents or adsorbents characterised by the absorbed or adsorbed substances
    • F01N3/0842Nitrogen oxides
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01NGAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N3/00Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
    • F01N3/08Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
    • F01N3/0807Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by using absorbents or adsorbents
    • F01N3/0871Regulation of absorbents or adsorbents, e.g. purging
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01NGAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N3/00Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
    • F01N3/08Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
    • F01N3/0807Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by using absorbents or adsorbents
    • F01N3/0871Regulation of absorbents or adsorbents, e.g. purging
    • F01N3/0885Regeneration of deteriorated absorbents or adsorbents, e.g. desulfurization of NOx traps
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02DCONTROLLING COMBUSTION ENGINES
    • F02D41/00Electrical control of supply of combustible mixture or its constituents
    • F02D41/02Circuit arrangements for generating control signals
    • F02D41/021Introducing corrections for particular conditions exterior to the engine
    • F02D41/0235Introducing corrections for particular conditions exterior to the engine in relation with the state of the exhaust gas treating apparatus
    • F02D41/024Introducing corrections for particular conditions exterior to the engine in relation with the state of the exhaust gas treating apparatus to increase temperature of the exhaust gas treating apparatus
    • F02D41/025Introducing corrections for particular conditions exterior to the engine in relation with the state of the exhaust gas treating apparatus to increase temperature of the exhaust gas treating apparatus by changing the composition of the exhaust gas, e.g. for exothermic reaction on exhaust gas treating apparatus
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02DCONTROLLING COMBUSTION ENGINES
    • F02D41/00Electrical control of supply of combustible mixture or its constituents
    • F02D41/02Circuit arrangements for generating control signals
    • F02D41/021Introducing corrections for particular conditions exterior to the engine
    • F02D41/0235Introducing corrections for particular conditions exterior to the engine in relation with the state of the exhaust gas treating apparatus
    • F02D41/027Introducing corrections for particular conditions exterior to the engine in relation with the state of the exhaust gas treating apparatus to purge or regenerate the exhaust gas treating apparatus
    • F02D41/0275Introducing corrections for particular conditions exterior to the engine in relation with the state of the exhaust gas treating apparatus to purge or regenerate the exhaust gas treating apparatus the exhaust gas treating apparatus being a NOx trap or adsorbent
    • F02D41/028Desulfurisation of NOx traps or adsorbent
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02DCONTROLLING COMBUSTION ENGINES
    • F02D41/00Electrical control of supply of combustible mixture or its constituents
    • F02D41/02Circuit arrangements for generating control signals
    • F02D41/021Introducing corrections for particular conditions exterior to the engine
    • F02D41/0235Introducing corrections for particular conditions exterior to the engine in relation with the state of the exhaust gas treating apparatus
    • F02D41/027Introducing corrections for particular conditions exterior to the engine in relation with the state of the exhaust gas treating apparatus to purge or regenerate the exhaust gas treating apparatus
    • F02D41/029Introducing corrections for particular conditions exterior to the engine in relation with the state of the exhaust gas treating apparatus to purge or regenerate the exhaust gas treating apparatus the exhaust gas treating apparatus being a particulate filter
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02DCONTROLLING COMBUSTION ENGINES
    • F02D41/00Electrical control of supply of combustible mixture or its constituents
    • F02D41/02Circuit arrangements for generating control signals
    • F02D41/04Introducing corrections for particular operating conditions
    • F02D41/08Introducing corrections for particular operating conditions for idling
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02DCONTROLLING COMBUSTION ENGINES
    • F02D41/00Electrical control of supply of combustible mixture or its constituents
    • F02D41/30Controlling fuel injection
    • F02D41/38Controlling fuel injection of the high pressure type
    • F02D41/40Controlling fuel injection of the high pressure type with means for controlling injection timing or duration
    • F02D41/402Multiple injections
    • F02D41/405Multiple injections with post injections
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02MSUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
    • F02M26/00Engine-pertinent apparatus for adding exhaust gases to combustion-air, main fuel or fuel-air mixture, e.g. by exhaust gas recirculation [EGR] systems
    • F02M26/13Arrangement or layout of EGR passages, e.g. in relation to specific engine parts or for incorporation of accessories
    • F02M26/22Arrangement or layout of EGR passages, e.g. in relation to specific engine parts or for incorporation of accessories with coolers in the recirculation passage
    • F02M26/23Layout, e.g. schematics
    • F02M26/28Layout, e.g. schematics with liquid-cooled heat exchangers
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01NGAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N2260/00Exhaust treating devices having provisions not otherwise provided for
    • F01N2260/14Exhaust treating devices having provisions not otherwise provided for for modifying or adapting flow area or back-pressure
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01NGAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N2570/00Exhaust treating apparatus eliminating, absorbing or adsorbing specific elements or compounds
    • F01N2570/04Sulfur or sulfur oxides
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02BINTERNAL-COMBUSTION PISTON ENGINES; COMBUSTION ENGINES IN GENERAL
    • F02B37/00Engines characterised by provision of pumps driven at least for part of the time by exhaust
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02MSUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
    • F02M26/00Engine-pertinent apparatus for adding exhaust gases to combustion-air, main fuel or fuel-air mixture, e.g. by exhaust gas recirculation [EGR] systems
    • F02M26/02EGR systems specially adapted for supercharged engines
    • F02M26/04EGR systems specially adapted for supercharged engines with a single turbocharger
    • F02M26/05High pressure loops, i.e. wherein recirculated exhaust gas is taken out from the exhaust system upstream of the turbine and reintroduced into the intake system downstream of the compressor
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02MSUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
    • F02M26/00Engine-pertinent apparatus for adding exhaust gases to combustion-air, main fuel or fuel-air mixture, e.g. by exhaust gas recirculation [EGR] systems
    • F02M26/02EGR systems specially adapted for supercharged engines
    • F02M26/09Constructional details, e.g. structural combinations of EGR systems and supercharger systems; Arrangement of the EGR and supercharger systems with respect to the engine
    • F02M26/10Constructional details, e.g. structural combinations of EGR systems and supercharger systems; Arrangement of the EGR and supercharger systems with respect to the engine having means to increase the pressure difference between the exhaust and intake system, e.g. venturis, variable geometry turbines, check valves using pressure pulsations or throttles in the air intake or exhaust system
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02MSUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
    • F02M26/00Engine-pertinent apparatus for adding exhaust gases to combustion-air, main fuel or fuel-air mixture, e.g. by exhaust gas recirculation [EGR] systems
    • F02M26/13Arrangement or layout of EGR passages, e.g. in relation to specific engine parts or for incorporation of accessories
    • F02M26/22Arrangement or layout of EGR passages, e.g. in relation to specific engine parts or for incorporation of accessories with coolers in the recirculation passage
    • F02M26/33Arrangement or layout of EGR passages, e.g. in relation to specific engine parts or for incorporation of accessories with coolers in the recirculation passage controlling the temperature of the recirculated gases
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02MSUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
    • F02M26/00Engine-pertinent apparatus for adding exhaust gases to combustion-air, main fuel or fuel-air mixture, e.g. by exhaust gas recirculation [EGR] systems
    • F02M26/52Systems for actuating EGR valves
    • F02M26/53Systems for actuating EGR valves using electric actuators, e.g. solenoids
    • Y02T10/26
    • Y02T10/44

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an exhaust gas purification device for an internal combustion engine, and more particularly to an exhaust gas purification device that can perform sulfur poisoning recovery even when extremely low load operation is continued.
[0002]
[Prior art]
In an internal combustion engine mounted on an automobile or the like, particularly in a diesel engine or lean burn gasoline engine that can burn an oxygen-rich mixture (so-called lean air-fuel mixture), it is included in the exhaust of the internal combustion engine A technique for purifying nitrogen oxide (NOx) is desired.
[0003]
In response to such demands, a technique for arranging a NOx absorbent in the exhaust system of an internal combustion engine has been proposed. As one of the NOx absorbents, it absorbs nitrogen oxides (NOx) in the exhaust when the oxygen concentration in the inflowing exhaust is high, and absorbs when the oxygen concentration in the inflowing exhaust is low and a reducing agent is present. Nitrogen (Nx) while releasing nitrogen oxide (NOx)2The NOx storage reduction catalyst is known to reduce to (3).
[0004]
When the NOx storage reduction catalyst is arranged in the exhaust system of the internal combustion engine, when the internal combustion engine is operated in lean combustion and the air-fuel ratio of the exhaust gas becomes high, nitrogen oxide (NOx) in the exhaust gas becomes the NOx storage reduction catalyst. When the air-fuel ratio of the exhaust gas that has been absorbed and flows into the NOx storage reduction catalyst becomes low, nitrogen oxide (NOx) that has been absorbed by the NOx storage reduction catalyst is released while nitrogen (N2).
[0005]
By the way, the NOx storage reduction catalyst absorbs sulfur oxide (SOx) produced by combustion of sulfur contained in fuel by the same mechanism as NOx. Since this sulfur oxide (SOx) is not released during the normal reduction and release of nitrogen oxide (NOx), when its accumulation exceeds a predetermined amount, a saturation state is caused and the NOx catalyst cannot absorb NOx. This is called sulfur poisoning (SOx poisoning), and the NOx purification rate decreases. Therefore, it is necessary to perform a poisoning recovery process for recovering the NOx catalyst from SOx poisoning at an appropriate time. This poisoning recovery process is performed by circulating exhaust gas with a reduced oxygen concentration through the NOx catalyst while keeping the NOx catalyst at a high temperature (eg, about 600 to 650 ° C.).
[0006]
However, since the exhaust gas during the lean combustion operation is lower than the above-described temperature, it is difficult to raise the NOx catalyst bed temperature to a temperature required for recovery from sulfur poisoning in a normal operation state. In such a case, by adding fuel to the exhaust passage, the oxygen concentration of the exhaust can be lowered while raising the temperature of the catalyst.
[0007]
As a method for increasing the temperature of the NOx catalyst, an exhaust purification device for an internal combustion engine described in Japanese Patent No. 2845056 has been proposed. The exhaust gas purification apparatus for an internal combustion engine described in this publication includes an amount of reducing agent consumed by reacting with oxygen in exhaust gas in the NOx storage reduction catalyst and nitrogen oxides absorbed in the NOx storage reduction catalyst ( In consideration of the amount of reducing agent required to reduce (NOx), the amount of reducing agent added is determined to prevent excessive supply or supply shortage of reducing agent, reducing agent and nitrogen oxide ( It is intended to suppress the deterioration of exhaust emission due to the release of NOx) into the atmosphere.
[0008]
On the other hand, in diesel engines, removal of particulate matter represented by soot, which is a suspended particulate matter contained in exhaust (Particulate Matter, hereinafter referred to as “PM” unless otherwise specified) is an important issue. For this reason, a technique of providing a particulate filter (hereinafter simply referred to as “filter”) for collecting PM in an exhaust system of a diesel engine so that PM is not released into the atmosphere is well known.
[0009]
This filter can prevent PM in the exhaust gas from being collected once and released into the atmosphere. However, when PM collected by the filter accumulates on the filter, the filter may be clogged. If this clogging occurs, the pressure of the exhaust gas upstream of the filter may increase, leading to a decrease in the output of the internal combustion engine and damage to the filter. In such a case, this PM can be removed by igniting and burning the PM deposited on the filter. The removal of PM deposited on the filter in this way is called filter regeneration.
[0010]
However, in order to ignite and burn the PM collected by the filter, the temperature of the filter needs to be set to a high temperature of, for example, 600 ° C. or more. However, since the exhaust temperature of the diesel engine is lower than this temperature, It was difficult to burn and remove PM in the state.
[0011]
Therefore, it is conceivable to heat and raise the temperature of the filter up to a temperature at which PM collected by an electric heater, burner or the like is generated, but this requires a large amount of energy to be supplied from the outside. To solve this problem, for example, according to Japanese Patent Laid-Open No. 6-159037, a filter carrying a NOx catalyst and a device for supplying hydrocarbons as a reducing agent into exhaust gas are used. PM can be easily burned by using the heat generated when burned with the NOx catalyst.
[0012]
By the way, the above-described sulfur poisoning recovery is performed by reducing the oxygen concentration in the exhaust gas. However, when a reducing agent is added during high load operation of the internal combustion engine, the reducing agent burns in the NOx storage reduction catalyst and this occlusion is performed. As a result of overheating of the reduced NOx catalyst, there is a risk of inducing thermal degradation of the NOx storage reduction catalyst. Therefore, it is preferable to perform sulfur poisoning recovery in a light load region.
[0013]
[Problems to be solved by the invention]
However, when the internal combustion engine is in an extremely low load operation state for a long time, for example, a vehicle equipped with this internal combustion engine has been parked in an idle state for a long time in a parking lot, or an urban area where traffic congestion is extremely heavy. When the vehicle is traveling, the exhaust gas discharged from the internal combustion engine is small, and the amount of heat generated by these is absolutely small, so the overall temperature of the filter (for example, having a capacity of 2 liters) carrying the NOx catalyst is raised. Insufficient heat for
[0014]
Even in a situation where the regeneration control of the PM accumulated in the filter and the sulfur poisoning regeneration control of the NOx catalyst should be performed in this state, the temperature of the NOx catalyst is raised to a region necessary for these controls. It is impossible to execute these controls. Therefore, there is a possibility that PM and NOx are not removed and exhaust purification is not sufficiently performed.
[0015]
The present invention has been made to solve the above-described problems. Even when the internal combustion engine is left in an extremely low load operation state, the PM captured by the filter and the sulfur poisoning regeneration control of the NOx catalyst are controlled. It aims to provide a technology that can be implemented.
[0016]
[Means for Solving the Problems]
In order to achieve the above object, the exhaust gas purification apparatus for an internal combustion engine of the present invention employs the following means. That is, when the air-fuel ratio of the inflowing exhaust gas is lean, the NOx in the exhaust gas is absorbed, and when the air-fuel ratio of the inflowing exhaust gas becomes the stoichiometric air-fuel ratio or rich, the NOx absorbent that releases the absorbed NOx is carried, and the internal combustion engine A filter capable of capturing particulates in the exhaust gas for a period of time, and capable of oxidizing and removing the particulates in a predetermined temperature range;
Depending on the operating state of the internal combustion engine, low temperature combustion, post injection, and fuel addition to the exhaust system are arbitrarily combinedFilter temperature control means for executing temperature rise control of the filter, and sulfur poisoning recovery control means for executing control for eliminating sulfur poisoning of the NOx absorbent, and oxidizing and / or removing the fine particles. When it is judged that the sulfur poisoning recovery control should be executed and the extremely low load state of the internal combustion engine has continued for a predetermined period or longer, the rotational speed of the internal combustion engine is increased by the temperature increase control. Then, the temperature of the filter is raised by the filter temperature control means to raise the temperature of the filter to a predetermined temperature to remove fine particles by oxidation and / or sulfur coverage of the NOx absorbent. It is characterized by carrying out sulfur poisoning recovery control for eliminating the poison.
[0017]
The most important feature of the present invention is that when the internal combustion engine has been in an extremely low load state for a predetermined period or longer, the filter needs to be subjected to oxidation removal of particulates or recovery from sulfur poisoning. Therefore, the rotational speed of the internal combustion engine is adjusted, and the temperature rise control is executed to raise the temperature of the filter to a predetermined temperature at which the above processing can be performed. After such processing is completed, fine particles can be oxidized and sulfur poisoning can be recovered.
[0018]
The air-fuel ratio of the exhaust refers to the weight ratio of air to fuel in the gas discharged to the exhaust passage due to combustion of the internal combustion engine, not the weight ratio of the air-fuel mixture sucked into the internal combustion engine.
[0019]
Here, when the internal combustion engine is in an extremely low load state is, for example, a case where the internal combustion engine is in an idling state.
[0020]
Further, adjusting the rotational speed of the internal combustion engine to reach a region where the temperature of the filter can be increased means that the rotational speed of the internal combustion engine is less than 1,000 rpm in an idling state or a state close thereto. For example, the rotational speed is increased to 1,200 rpm or more. The value of the rotational speed varies depending on the state of the internal combustion engine and other operating conditions, and is not constant.
[0021]
In this way, the amount of heat generated by first increasing the rotational speed of the internal combustion engine is increased, and the temperature is shifted to a rotation region in which the temperature of the filter can be increased by executing the temperature increase control.
[0022]
The temperature increase control executed thereafter can be performed by arbitrarily combining low-temperature combustion, post injection, and fuel addition to the exhaust system in accordance with the operating state of the internal combustion engine. For example, the temperature increase control for removing oxidation of fine particles is performed by one or a combination of two or more of low temperature combustion, post injection, and fuel addition to the exhaust system, and temperature increase control for sulfur poisoning recovery. Can be implemented by a combination of low temperature combustion and fuel addition to the exhaust system.
[0023]
Oxidation removal of the fine particles and sulfur poisoning recovery are performed when it is determined that each of these treatments is necessary. For example, the recovery of sulfur poisoning usually requires higher temperature of the filter (600 ° C or higher) than the oxidation removal of fine particles. Therefore, the filter bed temperature is raised to about 500 ° C to remove fine particles by oxidation. It may only run.
[0024]
In the oxidation removal of fine particles, for example, when a pressure gauge is installed before and after the filter and the exhaust pressure in the exhaust passage before and after the filter is measured and the differential pressure becomes a predetermined value or more, a predetermined amount of fine particles are present in the filter. It can be determined that the oxide removal treatment is necessary as a result of the above accumulation.
[0025]
Moreover, the following can be illustrated as a determination element of whether it is necessary to perform sulfur poisoning recovery | restoration control. That is, the determination can be made based on the integrated amount of fuel supplied to the engine, the amount of fuel added to the filter, the NOx flow detected by the NOx sensor downstream of the filter, or the vehicle travel distance mounted with the internal combustion engine.
[0026]
Also, the exhaust gas purification apparatus for an internal combustion engine of the present invention stores on the filter an active oxygen release agent that stores oxygen when excess oxygen exists in the surroundings and releases the stored oxygen as active oxygen when the surrounding oxygen concentration decreases. It is possible to carry and release active oxygen from the active oxygen release agent when the fine particles adhere to the filter, and oxidize and remove the fine particles attached on the filter by the released active oxygen.
[0027]
In such an exhaust gas purification apparatus for an internal combustion engine of the present invention, when the internal combustion engine is left in an extremely low load operating state, it is possible to oxidize and / or remove particulates that cannot be performed unless the filter is heated to a predetermined temperature. A series of means is provided for performing the sulfur poisoning recovery process of the NOx absorbent, and even under such circumstances, removal of particulates deposited on the filter and recovery of the sulfur poisoned NOx catalyst are possible.
[0028]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, specific embodiments of an exhaust emission control device for an internal combustion engine according to the present invention will be described with reference to the drawings. Here, the case where the exhaust gas purification apparatus for an internal combustion engine according to the present invention is applied to a diesel engine for driving a vehicle will be described as an example.
[0029]
FIG. 1 is a diagram showing a schematic configuration of an internal combustion engine 1 to which the exhaust gas purification apparatus according to the present embodiment is applied and its intake / exhaust system.
[0030]
An internal combustion engine 1 shown in FIG. 1 is a water-cooled four-cycle diesel engine having four cylinders 2.
[0031]
The internal combustion engine 1 includes a fuel injection valve 3 that injects fuel directly into the combustion chamber of each cylinder 2. Each fuel injection valve 3 is connected to a pressure accumulation chamber (common rail) 4 that accumulates fuel to a predetermined pressure. A common rail pressure sensor 4 a that outputs an electric signal corresponding to the fuel pressure in the common rail 4 is attached to the common rail 4.
[0032]
The common rail 4 communicates with a fuel pump 6 through a fuel supply pipe 5. The fuel pump 6 is a pump that operates using the rotational torque of the output shaft (crankshaft) of the internal combustion engine 1 as a drive source. A pump pulley 6 a attached to the input shaft of the fuel pump 6 is connected to the output shaft of the internal combustion engine 1 ( And a crank pulley 1a attached to the crankshaft) via a belt 7.
[0033]
In the fuel injection system configured as described above, when the rotational torque of the crankshaft is transmitted to the input shaft of the fuel pump 6, the fuel pump 6 transmits the rotational torque transmitted from the crankshaft to the input shaft of the fuel pump 6. The fuel is discharged at a pressure according to the pressure.
[0034]
The fuel discharged from the fuel pump 6 is supplied to the common rail 4 via the fuel supply pipe 5, accumulated in the common rail 4 up to a predetermined pressure, and distributed to the fuel injection valves 3 of each cylinder 2. When a drive current is applied to the fuel injection valve 3, the fuel injection valve 3 opens, and as a result, fuel is injected from the fuel injection valve 3 into the cylinder 2.
[0035]
Next, an intake branch pipe 8 is connected to the internal combustion engine 1, and each branch pipe of the intake branch pipe 8 communicates with a combustion chamber of each cylinder 2 via an intake port (not shown).
[0036]
The intake branch pipe 8 is connected to an intake pipe 9, and the intake pipe 9 is connected to an air cleaner box 10. The intake pipe 9 downstream of the air cleaner box 10 has an air flow meter 11 that outputs an electric signal corresponding to the mass of the intake air flowing through the intake pipe 9 and the temperature of the intake air flowing through the intake pipe 9. An intake air temperature sensor 12 for outputting the electrical signal is attached.
[0037]
An intake throttle valve 13 for adjusting the flow rate of the intake air flowing through the intake pipe 9 is provided in a portion of the intake pipe 9 located immediately upstream of the intake branch pipe 8. The intake throttle valve 13 is provided with an intake throttle actuator 14 that is configured by a step motor or the like and that drives the intake throttle valve 13 to open and close.
[0038]
The intake pipe 9 positioned between the air flow meter 11 and the intake throttle valve 13 is provided with a compressor housing 15a of a centrifugal supercharger (turbocharger) 15 that operates using the thermal energy of exhaust as a drive source. The intake pipe 9 downstream of the housing 15a is provided with an intercooler 16 for cooling the intake air that has been compressed in the compressor housing 15a and has reached a high temperature.
[0039]
In the intake system configured as described above, the intake air that has flowed into the air cleaner box 10 is removed through the intake pipe 9 after dust or dust in the intake air is removed by an air cleaner (not shown) in the air cleaner box 10. It flows into the compressor housing 15a.
[0040]
The intake air flowing into the compressor housing 15a is compressed by the rotation of the compressor wheel built in the compressor housing 15a. The intake air that has been compressed in the compressor housing 15a and has reached a high temperature is cooled by the intercooler 16, and then the flow rate is adjusted by the intake throttle valve 13 as necessary to flow into the intake branch pipe 8. The intake air that has flowed into the intake branch pipe 8 is distributed to the combustion chambers of the respective cylinders 2 through the respective branch pipes, and is burned using the fuel injected from the fuel injection valves 3 of the respective cylinders 2 as an ignition source.
[0041]
On the other hand, an exhaust branch pipe 18 is connected to the internal combustion engine 1, and each branch pipe of the exhaust branch pipe 18 communicates with a combustion chamber of each cylinder 2 via an exhaust port (not shown).
[0042]
The exhaust branch pipe 18 is connected to the turbine housing 15 b of the centrifugal supercharger 15. The turbine housing 15b is connected to an exhaust pipe 19, and the exhaust pipe 19 is connected to a muffler (not shown) downstream.
[0043]
In the middle of the exhaust pipe 19, a particulate filter (hereinafter simply referred to as a filter) 20 carrying an NOx storage reduction catalyst is provided. An exhaust gas temperature sensor 24 that outputs an electrical signal corresponding to the temperature of the exhaust gas flowing through the exhaust pipe 19 is attached to the exhaust pipe 19 upstream of the filter 20.
[0044]
A differential pressure sensor 37 is provided to detect a difference in pressure in the exhaust pipe 19 upstream and downstream of the filter 20.
[0045]
The exhaust pipe 19 downstream of the filter 20 is provided with an exhaust throttle valve 21 that adjusts the flow rate of the exhaust gas flowing through the exhaust pipe 19. The exhaust throttle valve 21 is provided with an exhaust throttle actuator 22 that is configured by a step motor or the like and that drives the exhaust throttle valve 21 to open and close.
[0046]
In the exhaust system configured as described above, the air-fuel mixture (burned gas) combusted in each cylinder 2 of the internal combustion engine 1 is discharged to the exhaust branch pipe 18 through the exhaust port, and then is centrifuged from the exhaust branch pipe 18. It flows into the turbine housing 15b of the feeder 15. The exhaust gas flowing into the turbine housing 15b rotates the turbine wheel that is rotatably supported in the turbine housing 15b using the thermal energy of the exhaust gas. At that time, the rotational torque of the turbine wheel is transmitted to the compressor wheel of the compressor housing 15a described above.
[0047]
Exhaust gas discharged from the turbine housing 15b flows into the filter 20 through the exhaust pipe 19, PM in the exhaust gas is collected, and harmful gas components are removed or purified. The exhaust gas from which PM has been collected by the filter 20 and from which harmful gas components have been removed or purified is adjusted in flow rate by the exhaust throttle valve 21 as necessary, and then released into the atmosphere via the muffler.
[0048]
Further, the exhaust branch pipe 18 and the intake branch pipe 8 have an exhaust recirculation passage (hereinafter referred to as an EGR passage) 25 for recirculating a part of the exhaust gas flowing through the exhaust branch pipe 18 to the intake branch pipe 8. It is communicated through. In the middle of the EGR passage 25, a flow rate adjusting valve is configured with an electromagnetic valve or the like, and changes the flow rate of exhaust gas (hereinafter referred to as EGR gas) flowing through the EGR passage 25 in accordance with the magnitude of applied power. (Hereinafter referred to as an EGR valve) 26 is provided.
[0049]
An EGR cooler 27 that cools the EGR gas flowing in the EGR passage 25 is provided in the middle of the EGR passage 25 and upstream of the EGR valve 26. The EGR cooler 27 is provided with a cooling water passage (not shown), and a part of the cooling water for cooling the internal combustion engine 1 circulates.
[0050]
In the exhaust gas recirculation mechanism configured as described above, when the EGR valve 26 is opened, the EGR passage 25 becomes conductive, and a part of the exhaust gas flowing through the exhaust branch pipe 18 flows into the EGR passage 25. Then, it is guided to the intake branch pipe 8 through the EGR cooler 27.
[0051]
At that time, in the EGR cooler 27, heat exchange is performed between the EGR gas flowing in the EGR passage 25 and the cooling water of the internal combustion engine 1, thereby cooling the EGR gas.
[0052]
The EGR gas recirculated from the exhaust branch pipe 18 to the intake branch pipe 8 through the EGR passage 25 is guided to the combustion chamber of each cylinder 2 while being mixed with fresh air flowing from the upstream side of the intake branch pipe 8.
[0053]
Here, the EGR gas contains water (H2O) and carbon dioxide (CO2) And the like, and since an inert gas component having a high heat capacity is not included, if the EGR gas is contained in the air-fuel mixture, the combustion temperature of the air-fuel mixture is lowered. Therefore, the amount of nitrogen oxide (NOx) generated is suppressed.
[0054]
Further, when the EGR gas is cooled in the EGR cooler 27, the temperature of the EGR gas itself is reduced and the volume of the EGR gas is reduced. Therefore, when the EGR gas is supplied into the combustion chamber, the atmosphere in the combustion chamber is reduced. The temperature does not rise unnecessarily, and the amount of fresh air (volume of fresh air) supplied into the combustion chamber is not unnecessarily reduced.
[0055]
In this embodiment, low temperature combustion is performed to increase the amount of EGR gas more than usual at light load, and PM removal, NOx purification, and temperature rise control of the filter 20 are executed. This low temperature combustion will be described. .
[0056]
As described above, conventionally, EGR has been used to suppress the generation of NOx. Since the EGR gas has a relatively high specific heat ratio and a large amount of heat is required to raise the temperature, the combustion temperature in the cylinder 2 decreases as the EGR gas ratio in the intake air increases. As the combustion temperature decreases, the amount of NOx generated also decreases. Therefore, the higher the EGR gas ratio, the lower the NOx emission.
[0057]
However, as the EGR gas ratio is increased, the generation amount of soot begins to increase abruptly at a certain ratio or more. Normal EGR control is performed at a lower EGR gas ratio than when soot begins to increase rapidly.
[0058]
However, as the EGR gas ratio is further increased, soot rapidly increases as described above, but there is a peak in the generation amount of this soot, and when the EGR gas ratio is further increased beyond this peak, This time, wrinkles start to decrease rapidly, and finally it hardly occurs.
[0059]
This is because when the temperature of the fuel during combustion in the combustion chamber and the surrounding gas is below a certain temperature, the growth of hydrocarbons (HC) stops at an intermediate stage before reaching soot, and the temperature of the fuel and the surrounding gas is reduced. This is because the hydrocarbon (HC) grows to soot all at once when the temperature rises above a certain temperature.
[0060]
Therefore, no soot is generated if the combustion during combustion in the combustion chamber and the surrounding gas temperature are suppressed below the temperature at which hydrocarbon (HC) growth stops midway. In this case, the temperature of the gas around the fuel is greatly influenced by the endothermic action of the gas around the fuel when the fuel burns, and the endothermic amount of the gas around the fuel according to the amount of heat generated during fuel combustion, that is, The occurrence of soot can be suppressed by adjusting the EGR gas ratio.
[0061]
The EGR gas ratio when performing low-temperature combustion is obtained in advance by experiments or the like and mapped, and stored in the ROM (352 in FIG. 5) in the ECU 35. Based on this map, EGR gas amount feedback control is performed.
[0062]
On the other hand, hydrocarbons (HC) that have stopped growing before reaching soot can be burned by an oxidant or the like carried on the filter 20.
[0063]
Thus, low temperature combustion is based on purifying hydrocarbons (HC) whose growth has stopped halfway before reaching soot with an oxidant or the like. Therefore, when the oxidant or the like is not activated, it is difficult to use low-temperature combustion because hydrocarbons (HC) are released into the atmosphere without being purified.
[0064]
Further, the temperature of the fuel during combustion in the cylinder 2 and the gas temperature around it can be controlled to a temperature below the temperature at which the growth of hydrocarbon (HC) stops halfway when the engine load is small and the amount of heat generated by combustion is small. It is.
[0065]
Therefore, in the present embodiment, the state in which the internal combustion engine 1 is operated at a low rotation and a low load continues, so that when the NOx storage reduction catalyst carried on the filter 20 reaches the active region, the temperature is low. Combustion control is performed. Whether it is in the active region or not can be determined based on an output signal of the exhaust temperature sensor 24 or the like.
[0066]
Thus, in low-temperature combustion, hydrocarbons (HC) as a reducing agent can be supplied to the NOx storage reduction catalyst while suppressing the emission of PM typified by soot, and NOx can be reduced and purified. The temperature of the filter 20 can be raised by the heat generated at this time.
[0067]
Therefore, in the present embodiment, low-temperature combustion is performed as necessary to raise the bed temperature of the filter 20, but the temperature rise control is executed by changing the air-fuel ratio according to the target temperature. That is, if the target temperature is high, the air-fuel ratio is set low, but this can be set to a desired air-fuel ratio by adjusting the EGR amount.
[0068]
The post-injection is intended to make the air-fuel ratio of the exhaust rich by injecting fuel in the expansion stroke or exhaust stroke after the main injection.
[0069]
Next, the filter 20 according to the present embodiment will be described.
[0070]
FIG. 2 is a cross-sectional view of the filter 20. FIG. 2A is a diagram illustrating a cross-section in the horizontal direction of the filter 20. FIG. 2B is a view showing a longitudinal section of the filter 20.
[0071]
As shown in FIG. 2A and FIG. 2B, the filter 20 is a so-called wall flow type including a plurality of exhaust flow passages 50 and 51 extending in parallel with each other. These exhaust flow passages include an exhaust inflow passage 50 whose downstream end is closed by a plug 52 and an exhaust outflow passage 51 whose upstream end is closed by a plug 53. In FIG. 2A, hatched portions indicate plugs 53. Therefore, the exhaust inflow passages 50 and the exhaust outflow passages 51 are alternately arranged via the thin partition walls 54. In other words, the exhaust inflow passage 50 and the exhaust outflow passage 51 are arranged such that each exhaust inflow passage 50 is surrounded by four exhaust outflow passages 51 and each exhaust outflow passage 51 is surrounded by four exhaust inflow passages 50.
[0072]
The filter 20 is made of a porous material such as cordierite, so that the exhaust gas flowing into the exhaust inflow passage 50 is adjacent to the surrounding partition wall 54 as shown by an arrow in FIG. To the exhaust outlet passage 51.
[0073]
In the embodiment according to the present invention, a carrier layer made of alumina, for example, is formed on the peripheral wall surfaces of each exhaust inflow passage 50 and each exhaust outflow passage 51, that is, on both side surfaces of each partition wall 54 and on the pore inner wall surface in each partition wall 54. The NOx storage reduction catalyst is supported on the carrier.
[0074]
Next, the function of the NOx storage reduction catalyst carried by the filter 20 according to the present embodiment will be described.
[0075]
The filter 20 uses, for example, alumina as a carrier, and an alkali metal such as potassium (K), sodium (Na), lithium (Li), or cesium (Cs), and barium (Ba) or calcium (Ca). ), An alkaline earth such as lanthanum (La) or yttrium (Y), and a noble metal such as platinum (Pt). In this embodiment, barium (Ba) and platinum (Pt) are supported on a support made of alumina, and O2Ceria with storage capability (Ce2OThree) Is added to the NOx storage reduction catalyst.
[0076]
Such NOx catalyst absorbs nitrogen oxide (NOx) in the exhaust when the oxygen concentration of the exhaust flowing into the NOx catalyst is high.
[0077]
On the other hand, the NOx catalyst releases the absorbed nitrogen oxide (NOx) when the oxygen concentration of the exhaust gas flowing into the NOx catalyst decreases. At that time, if a reducing component such as hydrocarbon (HC) or carbon monoxide (CO) is present in the exhaust, the NOx catalyst converts nitrogen oxide (NOx) released from the NOx catalyst to nitrogen (N2).
[0078]
By the way, when the internal combustion engine 1 is in a lean combustion operation, the air-fuel ratio of the exhaust discharged from the internal combustion engine 1 becomes a lean atmosphere, and the oxygen concentration of the exhaust becomes high. Therefore, nitrogen oxides (NOx) contained in the exhaust However, if the lean combustion operation of the internal combustion engine 1 is continued for a long period of time, the NOx absorption capacity of the NOx catalyst is saturated, and nitrogen oxides (NOx) in the exhaust gas are absorbed into the NOx catalyst. It remains in the exhaust without being removed.
[0079]
In particular, in the internal combustion engine 1 that is a diesel engine, the lean air-fuel ratio mixture is burned in the most operating region, and the air-fuel ratio of the exhaust gas becomes the lean air-fuel ratio in the most operating region accordingly. The NOx absorption capacity is easily saturated.
[0080]
Therefore, when the internal combustion engine 1 is operated in lean combustion, before the NOx absorption capacity of the NOx catalyst is saturated, the oxygen concentration in the exhaust gas flowing into the NOx catalyst is lowered and the concentration of the reducing agent is increased, so that the NOx catalyst is used. It is necessary to release and reduce the absorbed nitrogen oxides (NOx).
[0081]
As a method for reducing the oxygen concentration in this way, methods such as addition of fuel in the exhaust, low-temperature combustion, change of the fuel injection timing and the number of times into the cylinder 2, and the like can be considered. A reducing agent supply mechanism for adding fuel (light oil) as a reducing agent to exhaust gas flowing through the exhaust pipe 19 upstream from the filter 20 is provided. By adding fuel from the reducing agent supply mechanism into the exhaust gas, the filter 20 The oxygen concentration of the exhaust gas flowing in is reduced and the concentration of the reducing agent is increased.
[0082]
As shown in FIG. 1, the reducing agent supply mechanism is attached so that its injection hole faces the exhaust branch pipe 18, and is opened by a signal from the ECU 35 to inject fuel and a reducing agent injection valve 28. A reducing agent supply path 29 that guides the fuel discharged from the fuel pump 6 to the reducing agent injection valve 28, and a shutoff that is provided in the reducing agent supply path 29 and blocks the flow of fuel in the reducing agent supply path 29. And a valve 31.
[0083]
In such a reducing agent supply mechanism, high-pressure fuel discharged from the fuel pump 6 is applied to the reducing agent injection valve 28 via the reducing agent supply path 29. The reducing agent injection valve 28 is opened by a signal from the ECU 35, and fuel as a reducing agent is injected into the exhaust branch pipe 18.
[0084]
The reducing agent injected into the exhaust branch pipe 18 from the reducing agent injection valve 28 reduces the oxygen concentration of the exhaust gas flowing from the upstream side of the exhaust branch pipe 18.
[0085]
The exhaust gas having a low oxygen concentration formed in this way flows into the filter 20 and releases nitrogen oxide (NOx) absorbed by the filter 20 while nitrogen (N2).
[0086]
Thereafter, the reducing agent injection valve 28 is closed by a signal from the ECU 35, and the addition of the reducing agent into the exhaust branch pipe 18 is stopped.
[0087]
In this embodiment, the fuel is added by injecting the fuel into the exhaust gas. Instead, the amount of soot generated is increased to the maximum by increasing the amount of recirculated EGR gas. After that, low temperature combustion for further increasing the amount of EGR gas may be performed, or fuel may be injected from the fuel injection valve 3 during the expansion stroke, the exhaust stroke, or the like of the internal combustion engine 1.
[0088]
The internal combustion engine 1 configured as described above is provided with an electronic control unit (ECU) 35 for controlling the internal combustion engine 1. The ECU 35 is a unit that controls the operation state of the internal combustion engine 1 in accordance with the operation conditions of the internal combustion engine 1 and the request of the driver.
[0089]
Various sensors such as a common rail pressure sensor 4 a, an air flow meter 11, an intake air temperature sensor 12, an intake pipe pressure sensor 17, an exhaust gas temperature sensor 24, a crank position sensor 33, a water temperature sensor 34, and an accelerator opening sensor 36 are electrically wired to the ECU 35. And the output signals of the various sensors described above are input to the ECU 35.
[0090]
On the other hand, the ECU 35 is connected to the fuel injection valve 3, the intake throttle actuator 14, the exhaust throttle actuator 22, the reducing agent injection valve 28, the EGR valve 26, the shutoff valve 31 and the like via electrical wiring, The ECU 35 can be controlled.
[0091]
Here, as shown in FIG. 3, the ECU 35 includes a CPU 351, a ROM 352, a RAM 353, a backup RAM 354, an input port 356, and an output port 357, which are connected to each other by a bidirectional bus 350. , An A / D converter (A / D) 355 connected to the input port 356 is provided.
[0092]
The input port 356 receives an output signal from a sensor that outputs a digital signal format signal, such as the crank position sensor 33, and transmits the output signal to the CPU 351 and the RAM 353.
[0093]
The input port 356 is a signal in the form of an analog signal such as the common rail pressure sensor 4a, the air flow meter 11, the intake air temperature sensor 12, the intake pipe pressure sensor 17, the exhaust gas temperature sensor 24, the water temperature sensor 34, and the accelerator opening sensor 36. Are transmitted via the A / D 355 of the sensor that outputs the signal, and the output signals thereof are transmitted to the CPU 351 and the RAM 353.
[0094]
The output port 357 is connected to the fuel injection valve 3, the intake throttle actuator 14, the exhaust throttle actuator 22, the EGR valve 26, the reducing agent injection valve 28, the shutoff valve 31, etc. via electrical wiring, and is output from the CPU 351. The control signal is transmitted to the fuel injection valve 3, the intake throttle actuator 14, the exhaust throttle actuator 22, the EGR valve 26, the reducing agent injection valve 28, or the shutoff valve 31.
[0095]
The ROM 352 controls a fuel injection control routine for controlling the fuel injection valve 3, an intake throttle control routine for controlling the intake throttle valve 13, an exhaust throttle control routine for controlling the exhaust throttle valve 21, and an EGR valve 26. EGR control routine for performing, NOx purification control routine for releasing the absorbed NOx by adding a reducing agent to the filter 20, poisoning elimination control routine for eliminating SOx poisoning of the filter 20, and trapping by the filter 20 An application program such as a PM combustion control routine for burning and removing PM is stored.
[0096]
The ROM 352 stores various control maps in addition to the application programs described above. The control map is, for example, a fuel injection amount control map showing the relationship between the operating state of the internal combustion engine 1 and the basic fuel injection amount (basic fuel injection time), and the relationship between the operating state of the internal combustion engine 1 and the basic fuel injection timing. The fuel injection timing control map shown, the intake throttle valve opening control map showing the relationship between the operating state of the internal combustion engine 1 and the target opening of the intake throttle valve 13, the operating state of the internal combustion engine 1 and the target opening of the exhaust throttle valve 21 Exhaust throttle valve opening control map showing the relationship between the EGR valve opening control map showing the relationship between the operating state of the internal combustion engine 1 and the target opening of the EGR valve 26, the operating state of the internal combustion engine 1 and the reducing agent target Reducing agent addition amount control map showing the relationship with the addition amount (or exhaust target air-fuel ratio), reducing agent injection valve control map showing the relationship between the target addition amount of reducing agent and the opening time of the reducing agent injection valve 28, etc. It is.
[0097]
The RAM 353 stores output signals from the sensors, calculation results of the CPU 351, and the like. The calculation result is, for example, the engine speed calculated based on the time interval at which the crank position sensor 33 outputs a pulse signal. These data are rewritten to the latest data every time the crank position sensor 33 outputs a pulse signal.
[0098]
The backup RAM 354 is a nonvolatile memory capable of storing data even after the internal combustion engine 1 is stopped.
[0099]
The CPU 351 operates in accordance with an application program stored in the ROM 352, and executes fuel injection valve control, intake throttle control, exhaust throttle control, EGR control, NOx purification control, poisoning elimination control, PM combustion control, and the like.
[0100]
For example, in the NOx purification control, the CPU 351 executes so-called rich spike control in which the oxygen concentration in the exhaust gas flowing into the filter 20 is reduced in a spike manner (short time) in a relatively short cycle.
[0101]
In the rich spike control, the CPU 351 determines whether or not the rich spike control execution condition is satisfied every predetermined cycle. As this rich spike control execution condition, for example, the filter 20 is in an active state, the output signal value (exhaust temperature) of the exhaust temperature sensor 24 is equal to or lower than a predetermined upper limit value, poisoning elimination control is not executed, Etc. can be exemplified.
[0102]
When it is determined that the rich spike control execution condition as described above is satisfied, the CPU 351 controls the reducing agent injection valve 28 to inject fuel as a reducing agent from the reducing agent injection valve 28 in a spike manner. As a result, the air-fuel ratio of the exhaust gas flowing into the filter 20 is temporarily set to a predetermined target rich air-fuel ratio.
[0103]
Specifically, the CPU 351 stores the engine speed stored in the RAM 353, the output signal of the accelerator opening sensor 36 (accelerator opening), the output signal value of the air flow meter 11 (intake air amount), and the output of the air-fuel ratio sensor. Read signal, fuel injection amount, etc.
[0104]
The CPU 351 accesses the reducing agent addition amount control map in the ROM 352 using the engine speed, the accelerator opening, the intake air amount, and the fuel injection amount as parameters, and sets the air-fuel ratio of the exhaust to a preset target air-fuel ratio. The amount of addition of the reducing agent (target addition amount) required above is calculated.
[0105]
Subsequently, the CPU 351 accesses the reducing agent injection valve control map of the ROM 352 using the target addition amount as a parameter, and the reducing agent injection valve 28 necessary for injecting the reducing agent with the target addition amount from the reducing agent injection valve 28. The valve opening time (target valve opening time) is calculated.
[0106]
When the target valve opening time of the reducing agent injection valve 28 is calculated, the CPU 351 opens the reducing agent injection valve 28.
[0107]
When the target valve opening time has elapsed from the time when the reducing agent injection valve 28 is opened, the CPU 351 closes the reducing agent injection valve 28.
[0108]
Thus, when the reducing agent injection valve 28 is opened for the target valve opening time, a target addition amount of fuel is injected into the exhaust branch pipe 18 from the reducing agent injection valve 28. The reducing agent injected from the reducing agent injection valve 28 mixes with the exhaust gas flowing from the upstream side of the exhaust branch pipe 18 to form an air-fuel mixture having a target air-fuel ratio and flows into the filter 20.
[0109]
As a result, the air-fuel ratio of the exhaust gas flowing into the filter 20 changes in oxygen concentration in a relatively short cycle, and the filter 20 alternately repeats absorption and release / reduction of nitrogen oxide (NOx) in a short cycle. It will be.
[0110]
Next, in the poisoning elimination control, the CPU 351 executes a poisoning elimination process to eliminate the poisoning due to the oxide of the filter 20.
[0111]
Here, the fuel of the internal combustion engine 1 may contain sulfur (S), and when such fuel burns in the internal combustion engine 1, sulfur dioxide (SO2) And sulfur trioxide (SOThree) And other sulfur oxides (SOx).
[0112]
Sulfur oxide (SOx) flows into the filter 20 together with the exhaust gas, and is absorbed by the filter 20 by the same mechanism as nitrogen oxide (NOx).
[0113]
Specifically, when the oxygen concentration of the exhaust gas flowing into the filter 20 is high, sulfur dioxide (SO2) And sulfur trioxide (SOThree) And other sulfur oxides (SOx) are oxidized on the surface of platinum (Pt), and sulfate ions (SOFour 2-) Is absorbed by the filter 20. Furthermore, sulfate ions (SOFour 2-) Combines with barium oxide (BaO) to form sulfate (BaSO).Four).
[0114]
By the way, sulfate (BaSOFour) Is barium nitrate (Ba (NOThree)2) And is difficult to decompose, and even if the oxygen concentration of the exhaust gas flowing into the filter 20 is lowered, it remains in the filter 20 without being decomposed.
[0115]
Sulfate (BaSOFour) Increases accordingly, the amount of barium oxide (BaO) that can participate in the absorption of nitrogen oxides (NOx) decreases accordingly, so that the NOx absorption capacity of the filter 20 decreases, so-called sulfur poisoning. Will occur.
[0116]
As a method for eliminating sulfur poisoning of the filter 20, the temperature of the atmosphere of the filter 20 is raised to a high temperature range of approximately 600 to 650 ° C., and the oxygen concentration of the exhaust gas flowing into the filter 20 is lowered to reduce the filter 20. Barium sulfate (BaSOSO)Four) SOThree -And SOFour -Pyrolyzed, and then SOThree -And SOFour -Reacts with hydrocarbons (HC) and carbon monoxide (CO) in the exhaust to produce gaseous SO2 -An example of the method for reduction is shown.
[0117]
Therefore, in the poisoning elimination process according to the present embodiment, the CPU 351 first performs the catalyst temperature increase control for increasing the bed temperature of the filter 20 and then reduces the oxygen concentration of the exhaust gas flowing into the filter 20. .
[0118]
In the catalyst temperature increase control, the CPU 351, for example, injects fuel from the fuel injection valve 3 at the time of the expansion stroke of each cylinder 2 and adds the fuel from the reducing agent injection valve 28 into the exhaust gas. The unburned fuel component may be oxidized in the filter 20, and the bed temperature of the filter 20 may be increased by the heat generated during the oxidation.
[0119]
However, if the temperature of the filter 20 is excessively increased, thermal degradation of the filter 20 may be induced. Therefore, the secondary injected fuel amount and the added fuel amount are feedback controlled based on the output signal value of the exhaust temperature sensor 24. It is preferable to do so.
[0120]
When the bed temperature of the filter 20 rises to a high temperature range of about 600 ° C. to 650 ° C. by the catalyst temperature raising process as described above, the CPU 351 starts from the reducing agent injection valve 28 to reduce the oxygen concentration of the exhaust gas flowing into the filter 20. Inject fuel.
[0121]
When excessive fuel is injected from the reducing agent injection valve 28, the fuel is burnt rapidly in the filter 20 and the filter 20 is overheated, or the excess fuel injected from the reducing agent injection valve 28 filters the fuel. Therefore, it is preferable that the CPU 351 feedback-controls the fuel injection amount from the reducing agent injection valve 28 based on an output signal of an air-fuel ratio sensor (not shown).
[0122]
When the poisoning recovery process is executed in this way, the oxygen concentration of the exhaust gas flowing into the filter 20 becomes low under a situation where the bed temperature of the filter 20 is high. Then, barium sulfate (BaSO4) absorbed in the filter 20 is obtained.Four) Is SOThree -And SOFour -Pyrolysis into these SOThree -And SOFour -Reacts with hydrocarbons (HC) and carbon monoxide (CO) in the exhaust gas and is reduced, so that sulfur poisoning of the filter 20 is eliminated.
[0123]
Next, the flow of temperature increase control and sulfur poisoning recovery control according to the present embodiment will be described.
[0124]
FIG. 5 is a flowchart showing a flow of temperature increase control according to the present embodiment.
[0125]
First, this control is started when there is a situation in which particulate removal by oxidation (hereinafter referred to as PM regeneration) or sulfur poisoning recovery is to be performed, that is, when a flag for executing these controls is set. To do.
[0126]
As a starting condition, in the case of sulfur poisoning regeneration, determination is made based on an accumulated fuel consumption, an output signal from a NOx sensor (not shown), a vehicle travel distance, and the like. Here, since the NOx storage reduction catalyst carried on the filter 20 is poisoned by the sulfur component in the fuel, the accumulated amount of fuel consumption is stored in the RAM 353, and when the amount of fuel addition reaches a predetermined amount. It may be a start condition for sulfur poisoning recovery control. Further, as sulfur poisoning proceeds, the amount of NOx absorbed by the NOx storage reduction catalyst decreases, and the amount of NOx flowing downstream of the filter 20 increases. Therefore, a NOx sensor (not shown) may be provided downstream of the filter 20, and this output signal may be monitored, and the start condition of the sulfur poisoning recovery control may be when the flow rate of NOx exceeds a predetermined amount. Further, when the vehicle travel distance exceeds a predetermined value, it is determined that the sulfur poisoning needs to be restored, and a sulfur poisoning recovery control flag is set at this time.
[0127]
In the case of PM regeneration, for example, when the differential pressure in the exhaust pipe 19 before and after the filter 20 detected by the differential pressure sensor 37 exceeds a predetermined value, a certain amount or more of PM has accumulated on the filter 20. Can be estimated. If a certain amount or more of PM accumulates in this way, a PM regeneration control flag is set.
[0128]
If these sulfur poisoning regeneration or PM regeneration flags are set, the process proceeds to step S101.
[0129]
In step S101, it is determined whether or not the internal combustion engine 1 is in a light load state. If it is not in the light load state, it is determined that it is not necessary to perform PM regeneration or the like based on the temperature increase control, and this routine is terminated.
[0130]
On the other hand, if it is a light load state, it will progress to step S102. In step S102, it is determined whether or not the bed temperature of the filter 20 is less than 150 ° C. The temperature of the filter 20 is estimated by an exhaust temperature sensor 24 provided in the exhaust pipe 19 immediately before the filter 20. When the temperature of the filter 20 is less than 150 ° C., the catalyst is not activated and effective exhaust purification cannot be performed.
[0131]
When the bed temperature of the filter 20 is lower than 150 ° C., the process proceeds to step S103.
On the other hand, if the temperature is 150 ° C. or higher, this control ends. In this case, oxidation removal of fine particles and recovery from sulfur poisoning may be performed by normal temperature increase control or the like.
[0132]
In step S103, it is determined whether or not the light load and the bed temperature of the filter 20 have been left for a predetermined time or longer in a state of less than 150 ° C. In this case, how much the fixed time is set is determined in consideration of various circumstances, and can be set to 15 minutes, for example.
[0133]
If it has been left for a certain period of time or longer, the process proceeds to step S104. On the contrary, if it has not been left for a certain period of time or longer, this control is once terminated.
[0134]
In step S104, it is determined whether or not the state of the internal combustion engine 1 is idling. If the rotational speed of the internal combustion engine 1 is, for example, about 750 rpm, it is determined that the engine is idling, and the process proceeds to step S106. On the other hand, when it is not in the idling state, the process proceeds to step S105, and early warm-up combustion is executed.
[0135]
In S106, the rotational speed of the internal combustion engine 1 is increased to 1,200 rpm and early warm-up combustion is performed, and then the process proceeds to Step S107.
[0136]
Here, the early warm-up combustion is for increasing the temperature of the filter 20 and can be exemplified by the following method.
[0137]
First, in the combustion of the internal combustion engine 1, the fuel injection timing is retarded until after the compression top dead center. In normal combustion, the main fuel is injected in the vicinity of the compression top dead center. However, if the injection timing is retarded, the afterburning period becomes longer, and the exhaust temperature rises. As the exhaust gas temperature rises, the temperature of the filter 20 rises.
[0138]
Second, there is a method of additionally injecting auxiliary fuel in the vicinity of the intake top dead center in addition to the main fuel. Such additional injection of auxiliary fuel is hereinafter referred to as post-injection. According to this post-injection, the fuel to be injected increases, so the exhaust temperature rises and the temperature of the filter 20 can be raised.
[0139]
In such post-injection near the intake top dead center, intermediate products such as aldehyde, ketone, peroxide, carbon monoxide, and the like are generated by the post-injection due to the compression heat during the compression stroke, and are mainly injected later. Fuel reaction is accelerated. In this case, even if the injection timing of the main fuel is delayed, misfire does not occur and good combustion can be obtained. Therefore, the exhaust temperature can be raised by delaying the injection timing of the main fuel. Therefore, the temperature of the filter 20 can be raised.
[0140]
Third, in addition to the main fuel injection, post injection is performed during the expansion stroke or the exhaust stroke. In this case, most of the post-injection fuel is discharged into the exhaust pipe in the form of unburned hydrocarbon (HC). This unburned hydrocarbon (HC) is oxidized on the filter 20, and the temperature of the filter 20 rises due to the oxidation reaction heat generated at this time.
[0141]
Next, in step S107, it is determined whether the bed temperature of the filter 20 is 180 ° C. or higher. When the bed temperature is 180 ° C. or higher, the process proceeds to step S108.
[0142]
On the other hand, if the bed temperature is less than 180 ° C., the process returns to step S106, and the early warm-up combustion is continued while maintaining the rotational speed of the internal combustion engine at 1,200 rpm.
[0143]
In step S108, it is determined whether or not the water temperature is 60 ° C. or higher. If the water temperature is 60 ° C. or higher, the process proceeds to step S109, where weak lean low-temperature combustion (air-fuel ratio is around 18) is executed as the temperature raising means of the filter 20. The low-temperature combustion here is combustion at an air-fuel ratio that is lower than the air-fuel ratio of combustion in the normal internal combustion engine 1, and hydrocarbon (HC) components in the fuel are combusted by the filter 20. Rises.
[0144]
The air / fuel ratio can be adjusted to a desired value by changing the EGR amount.
[0145]
On the other hand, if the water temperature is lower than 60 ° C., the process proceeds to step S111 and post injection is executed as a temperature raising means.
[0146]
The reason why the temperature raising means of these filters 20 is selectively used according to the water temperature is to stabilize the combustion of the internal combustion engine 1. That is, if the water temperature is 60 ° C. or higher, the temperature rise by low temperature combustion is stable, but if the water temperature is less than 60 ° C., the low temperature combustion becomes unstable. If the water temperature is 60 ° C. or higher, the reason for adopting low temperature combustion is that the amount of fuel injection in the post-injection in a light load state is small, and it is assumed that this is injected in multiple times. This is because it is difficult to control the injection amount, and thus temperature rise control by low-temperature combustion is preferable.
[0147]
As described above, the temperature rise control is preferably performed by low temperature combustion as much as possible because the stability of combustion is easily obtained. However, when the water temperature is less than 60 ° C., the combustion state is caused by post injection rather than low temperature combustion. It can be maintained well.
[0148]
It is desirable that the temperature increase control of the filter 20 by adding fuel is not performed as much as possible in the region where the bed temperature of the filter 20 is low. The reason is to avoid a situation where the added fuel adheres to the wall surface of the exhaust pipe in a situation where the temperature of the added fuel is low. Therefore, it is preferable to employ low-temperature combustion or post-injection that does not cause such a situation as the temperature increase control means executed here.
[0149]
After performing low temperature combustion in step S109, in step S110, it is determined whether or not the bed temperature of the filter 20 is 300 ° C. or higher.
[0150]
On the other hand, when post injection is executed in step S111, it is similarly determined in step S112 whether the bed temperature of the filter 20 is 300 ° C. or higher.
[0151]
If the bed temperature is lower than 300 ° C. in step S110, the process returns to step S109, and the weak lean low temperature combustion is continued.
[0152]
When the bed temperature is lower than 300 ° C. in step S112, the process returns to step S111 and the post injection is continued.
[0153]
If the bed temperature is 300 ° C. or higher in step S110, the process proceeds to step S114, and weak lean low-temperature combustion is continued with a lower air-fuel ratio than the previous low-temperature combustion. Here, the air-fuel ratio is adjusted to around 16.
[0154]
If the bed temperature is 300 ° C. or higher in step S112, the process proceeds to step S113, and it is determined whether or not the water temperature is 60 ° C. or higher. If the water temperature is 60 ° C. or higher, post-injection is stopped, and the process proceeds to step S114 to shift to weak lean low-temperature combustion.
[0155]
If the water temperature is lower than 60 ° C. in step S113, the process proceeds to step S115, and temperature increase control for adding fuel to the exhaust system is performed.
[0156]
Next, after the low temperature combustion in S114 is continued for a certain time, the process proceeds to S116, and it is determined whether or not the bed temperature of the filter 20 has become 500 ° C. or higher.
[0157]
When fuel addition is executed in S115, the process proceeds to S117 after elapse of a predetermined time, and it is determined whether or not the bed temperature of the filter 20 is 500 ° C. or higher.
[0158]
In step S116, when the bed temperature of the filter 20 has not reached 500 ° C., the process returns to step S114, and the weak lean low-temperature combustion is continued.
[0159]
Similarly, in step S117, when the bed temperature of the filter 20 has not reached 500 ° C., the process returns to step S115, and further fuel addition is executed.
[0160]
When the bed temperature of the filter 20 is 500 ° C. or higher in step 116, it is determined that PM regeneration has been performed when the differential pressure is reduced to a predetermined value or less by the differential pressure sensor 37, and it is necessary to regenerate sulfur poisoning. If there is no flag, that is, if the sulfur poisoning regeneration flag is not set, this control is terminated.
[0161]
Similarly, if the bed temperature of the filter 20 is 500 ° C. or higher in step 117, it is determined that PM regeneration has been performed when the pressure regeneration is continued and the differential pressure becomes a predetermined value or less by the differential pressure sensor 37. . Then, when the sulfur poisoning regeneration is not necessary, that is, when the sulfur poisoning regeneration flag is not set, this control is terminated.
[0162]
On the other hand, when the sulfur poisoning regeneration flag is set, the routine proceeds to step S118, where sulfur poisoning regeneration control is executed. Here, in order to raise the temperature of the filter 20 to 600 ° C., weak lean low temperature combustion and fuel addition are performed.
[0163]
Next, it progresses to step S119 and it is judged whether the bed temperature of the filter 20 is 600 degreeC or more. When the bed temperature is 600 ° C. or higher, the process proceeds to step S122, and it is determined whether or not the sulfur poisoning recovery control has continued for a predetermined time or longer, for example, 3 minutes or longer. On the other hand, when the bed temperature is lower than 600 ° C., the process proceeds to step S120, and it is determined whether or not the air-fuel ratio is smaller than the stoichiometric (theoretical air-fuel ratio). When the air-fuel ratio is leaner than stoichiometric, the process returns to step S118, and further the temperature increase control for sulfur poisoning recovery is continued. On the contrary, if the air-fuel ratio is stoichiometric or rich, the process proceeds to step S121, and fuel addition is stopped for a certain period. In this state, it is presumed that oxygen does not exist in the exhaust gas, and the fuel does not burn even if more fuel is added. Therefore, after a predetermined period elapses, oxygen is present in the exhaust gas. Returning, further, low temperature combustion and fuel addition are executed to continue temperature increase control for sulfur poisoning recovery.
[0164]
In step S122, if the sulfur poisoning recovery control is executed for a predetermined time or longer, that is, for a total of 3 minutes or longer, this control is terminated assuming that the sulfur poisoning recovery of the catalyst has been performed.
[0165]
In step S122, when the sulfur poisoning recovery control is not executed for a total of 3 minutes or more, this control is further continued. When the control execution time is a total of 3 minutes or more, this control is terminated.
[0166]
As described above, in the exhaust gas purification apparatus for an internal combustion engine according to the present embodiment, the flag for sulfur poisoning regeneration control and PM regeneration control is set under a situation where the internal combustion engine is in an idle state and a certain period of time elapses. If so, these controls can be executed reliably in accordance with the above procedure. The filter bed temperature is raised stepwise while executing a combination of the most appropriate methods according to the operating state of the internal combustion engine, the water temperature, etc. Regeneration control and sulfur poisoning recovery control can be performed.
[0167]
【The invention's effect】
According to the exhaust gas purification apparatus for an internal combustion engine according to the present invention, a filter that carries a catalyst for NOx purification and is capable of capturing PM even at a predetermined temperature even when the internal combustion engine continues to operate at an extremely low load. The temperature can be raised to the region. Therefore, even under such circumstances, removal of PM captured by the filter and sulfur poisoning regeneration control of the NOx catalyst can be reliably executed.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram showing a diesel engine to which an exhaust gas purification apparatus for an internal combustion engine according to an embodiment of the present invention is applied and an intake / exhaust system thereof.
FIG. 2A is a diagram showing a transverse cross section of a particulate filter. (B) is a figure which shows the longitudinal direction cross section of a particulate filter.
FIG. 3 is a block diagram showing an internal configuration of an ECU.
FIG. 4 is a diagram showing the relationship between the bed temperature of the filter and PM combustion.
FIG. 5 is a flowchart showing a flow of temperature increase control execution according to the present invention.
[Explanation of symbols]
1 ... Internal combustion engine
1a ... Crank pulley
2. Cylinder
3. Fuel injection valve
4 ... Common rail
4a ... Common rail pressure sensor
5. Fuel supply pipe
6. Fuel pump
6a ... Pump pulley
8 ... Intake branch pipe
9. Intake pipe
18 ... Exhaust branch pipe
19 ... Exhaust pipe
20 ... Particulate filter
21 ... Exhaust throttle valve
24 ... Exhaust temperature sensor
25 ... EGR passage
26 ... EGR valve
27 ... EGR cooler
28 ... Reducing agent injection valve
29 ... Reducing agent supply path
31 ... Shut-off valve
33 ... Crank position sensor
34 ... Water temperature sensor
35 ... ECU
36 Accelerator opening sensor
37 ... Differential pressure sensor

Claims (3)

  1. When the air-fuel ratio of the inflowing exhaust gas is lean, the NOx in the exhaust gas is absorbed, and when the air-fuel ratio of the inflowing exhaust gas becomes the stoichiometric air-fuel ratio or rich, the NOx absorbent that releases the absorbed NOx is carried, and in the exhaust gas of the internal combustion engine A filter capable of capturing the particulates for a period of time, and capable of oxidizing and removing the particulates in a predetermined temperature range;
    Filter temperature control means for performing temperature increase control of the filter, which is implemented by arbitrarily combining low temperature combustion, post injection, and fuel addition to the exhaust system according to the operating state of the internal combustion engine, and sulfur of the NOx absorbent Sulfur poisoning recovery control means for executing control for eliminating poisoning, and it is determined that the oxidation removal of the fine particles and / or sulfur poisoning recovery control should be executed, and the pole of the internal combustion engine When the low load state continues for a predetermined period or longer, the rotational speed of the internal combustion engine is adjusted so as to reach a region where the temperature of the filter can be increased by the temperature increase control, and then increased by the filter temperature control means. The temperature control is executed to increase the temperature of the filter to a predetermined temperature, and the sulfur poisoning recovery control is performed to remove particulates by oxidation and / or to eliminate sulfur poisoning of the NOx absorbent. Exhaust purification system of an internal combustion engine to be.
  2. The temperature increase control for oxidation removal of fine particles is performed by one or a combination of two or more of low temperature combustion, post injection, and fuel addition to the exhaust system, and the temperature increase control for sulfur poisoning recovery 2. The exhaust gas purification apparatus for an internal combustion engine according to claim 1 , wherein the operation is performed by a combination of low temperature combustion and fuel addition to the exhaust system.
  3. Oxygen is occluded when excess oxygen is present in the surroundings, and an active oxygen release agent that releases occluded oxygen as active oxygen is carried on the filter when the surrounding oxygen concentration decreases, and when fine particles adhere to the filter 3. The exhaust emission control device for an internal combustion engine according to claim 1, wherein active oxygen is released from the active oxygen release agent and fine particles adhering to the filter are oxidized and removed by the released active oxygen.
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JP2001317222A JP3835241B2 (en) 2001-10-15 2001-10-15 Exhaust gas purification device for internal combustion engine
CA002463696A CA2463696C (en) 2001-10-15 2002-10-14 Exhaust gas purifying device and method for internal combustion engine
AT02801452T AT382785T (en) 2001-10-15 2002-10-14 Exhaust gas cleaning device and method for internal combustion engine
DE60224430T DE60224430T2 (en) 2001-10-15 2002-10-14 Exhaust gas cleaning device and method for internal combustion engine
ES02801452T ES2297049T3 (en) 2001-10-15 2002-10-14 Exhaust gas purification device and method for internal combustion engine.
EP02801452A EP1444430B1 (en) 2001-10-15 2002-10-14 Exhaust gas purifying device and method for internal combustion engine
PCT/IB2002/004200 WO2003033892A1 (en) 2001-10-15 2002-10-14 Exhaust gas purifying device and method for internal combustion engine
KR1020047005533A KR100613646B1 (en) 2001-10-15 2002-10-14 Exhaust gas purifying device and method for internal combustion engine
US10/491,721 US7246485B2 (en) 2001-10-15 2002-10-14 Exhaust gas purifying device and method for internal combustion engine

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KR20050036860A (en) 2005-04-20
EP1444430A1 (en) 2004-08-11
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KR100613646B1 (en) 2006-08-17
WO2003033892A1 (en) 2003-04-24

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